This invention relates to active hydrogen containing compositions useful in preparing polyurethane polymers, particularly low resiliency polyurethane foams.
In preparing flexible polyurethane and/or polyurea foams, it is necessary that the polymer foam be open-celled. The presence of closed cells substantially reduces the dimensional stability and flexibility of the foam while increasing the rigidity and brittleness. Since high flexibility and dimensional stability are essential properties of these foams, the foam formulation and/or processing conditions must be such to promote the formation of open-cells.
Various additives which promote cell-opening are known. For example, the so-called polymer polyols (also copolymer polyols) are sometimes used in polyurethane foam formulations to promote cell opening. However, polymer polyols are not generally useful for preparing low resiliency foams.
Polyolefins, particularly polybutene, and waxy aliphatic hydrocarbons such as paraffin oil are the most commonly employed cell openers in low resiliency foams. Unfortunately, these materials are incompatible with the reactants used in making the foam or with the product foam itself. This incompatibility leads to several problems. The polyolefin or waxy hydrocarbon cannot be formulated into the polyol or polyisocyanate blends used to prepare the foam, since it will rapidly phase separate. Thus, these cell openers must be metered separately into the foam formulation simultaneously with or immediately prior to start of the foaming reaction. In addition, since these cell openers are incompatible with the product foam, they tend to leach out of the foam with time.
Another problem with conventional cell openers is the amount required to be effective. Since these cell openers do not contribute to the overall properties of the foam, except to open cells, it is desirable to reduce, the required amount of cell opener, whenever possible.
The production of low resiliency foams provides additional problems. Low resiliency foams are generally prepared using polyols of moderate (i.e. 500-1200) molecular weight rather than the higher molecular weight polyols used in higher resiliency foams. In reacting with a polyisocyanate, the moderate molecular weight polyols form cells which are more difficult to open than those prepared from higher molecular weight polyols. Thus, the preparation of low resiliency foams particularly requires an especially effective cell opener.
Accordingly, it would be desirable to provide a cell opening additive which is compatible with the reactants used in preparing flexible foam and/or the foam itself. Preferably, such cell opening additive is one which is effective at relatively low levels of use. In addition, it would be desirable to provide a cell opening additive which is suitable for use in preparing low resiliency foams.